The invention relates to a tire chain with a net configuration having nodal points, in which at least three chain links are mutually connected in the region of the nodal points via a component which is arranged horizontally, that is to say parallel to the tire surface, and is provided with hook-shaped holding arms and insertion slots for hanging the chain links in and with at least one closure element for the insertion slots.
In tire chains of the above type, the components arranged in the region of the nodal points are of decisive importance for the strength, mounting, repairs and functional suitability of the chain. Not least for this reason have numerous solutions been developed in endeavours to meet the demands made to the greatest possible extent.
Most widely used are tire chains, in which the components, arranged horizontally at the nodal points, are formed by chain joints having a base body, the shape of which is adapted to the shape of round or oval chain links and which is provided with a closable insertion slot for the chain links to be hung in. In these chain joints, three and more chain links are held in one and the same holder; this is associated with a considerable load on the base body and virtually inevitably requires at least frictional bridging of the ends limiting the insertion slot.
A chain joint of the type indicated is known, for example, from German Auslegeschrift No. 1,283,613. It has a cross-section which entails a comparatively severe restriction of the mobility of the net parts located between the nodal points. To bridge and close the insertion slot, clamping elements which can be screwed together and act frictionally are used in this chain joint; these clamping elements have all the disadvantages caused by unwanted loosening of the screwed connection serving to apply the clamping force.
A chain joint of similar construction, with a clamping connection assisted by positive engagement, is shown by German Utility Model No. 1,971,292. Although the positive engagement here improves the strength of the connection, the risk of unintended loosening remains. A further disadvantage in both the constructions mentioned is that a relatively large number of parts is required for closing the insertion slot, which are moreover located in the wearing zone of the tire chain.
The arrangement of the closure elements of the chain joint according to German Patent Specification No. 2,112,440 is more favourable with regard to wear, since in this joint the screw used for firmly clamping the closure elements has been moved into the plane of the joint. However, the risk of loosening of the screwed connection is still present in this case.
The chain joint according to German Patent Specification No. 1,605,672 manages without a screwed connection supplying the clamping forces; in this case, a closure piece is used which is provided with two bores delimiting the insertion slot and receiving the angled ends of an annular base body. To secure the closure piece, braces are used here, which are subjected to considerable stresses due to an unfavourable arrangement and tend to shear off after the tire chain has been used for a certain period.
A further common disadvantage of all the solutions so far described is that all the chain links to be hung in must be hung at one and the same point into the base body of the chain joints located at the nodal points; this makes it considerably more difficult to join the end links of the chain strands running in different directions from the nodal points, especially in the case of heavy tire protection chains.
A tire chain of the generic type described initally, in which the hanging in of the chain links to be connected to the nodal points is facilitated by the use of components with several insertion slots, is known from U.S. Patent Specification No. 1,806,064. The component arranged in the region of the nodal points is here formed by two parallel plates mounted on a common pivot journal, the edge of the plates being provided with four substantially L-shaped insertion slots. The arrangement of the insertion slots is here such that the chain links can be locked by rotating the superimposed plates, a rivet connecting the plates with one another in the locked state, and locking cams and locking gaps on the mutually facing plate surfaces effecting a retention of the plates in the locked position. The known construction is not really satisfactory, inasmuch as the manufacture of the plates is expensive and their handling and locking on mounting the chains are laborious. Moreover, the strength of the components leaves something to be desired, and the space requirement of the components is large.